如何将数据从订阅存储/设置到外部变量，并再次从Angular 7中的其他类读取数据

import { Injectable } from '@angular/core';
import { BehaviorSubject } from 'rxjs';

@Injectable({
  providedIn: 'root'
})
export class DataService {
  private dataSubject: BehaviorSubject<any> = new BehaviorSubject<any>(null);
  public data$ = this.dataSubject.asObservable();

  setData(data: any) {
    this.dataSubject.next(data);
  }
}

import { Component } from '@angular/core';
import { DataService } from 'path-to-data-service';

@Component({
  selector: 'app-source-component',
  template: `
    <button (click)="setData()">Set Data</button>
  `
})
export class SourceComponent {
  constructor(private dataService: DataService) {}

  setData() {
    const data = 'Hello, World!';
    this.dataService.setData(data);
  }
}

import { Component, OnInit } from '@angular/core';
import { DataService } from 'path-to-data-service';

@Component({
  selector: 'app-destination-component',
  template: `
    <p>Data: {{ data }}</p>
  `
})
export class DestinationComponent implements OnInit {
  data: any;

  constructor(private dataService: DataService) {}

  ngOnInit() {
    this.dataService.data$.subscribe(data => {
      this.data = data;
    });
  }
}